Concrete building block



FIG. 1 is a perspective view of a concrete building block showing my newdesign;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a top view thereof;

FIG. 5 is a bottom view thereof;

FIG. 6 is a right side view thereof;

FIG. 7 is a left side view thereof; and,

FIG. 8 is a cross-sectional view taken along lines 8-8 of FIG. 2thereof.

The broken lines illustrate portions of the concrete building blockwhich form no part of the claimed design.

CLAIM The ornamental design for a concrete building block, as shown anddescribed.